Prescribed Metformin but never tested for PCOS...is this routine?

That pretty much says it all. I have been trying to get pregnant for 8 months now and nada. I have very irregular periods (2 months apart, mostly heavy bleeding lasting for 2 weeks). My doctor (Kaiser) didn't do any testing for PCOS before they prescribed me Metformin. Is this normal? I don't entirely feel comfortable taking drugs for something I haven't been officially diagnosed for. Thanks. By the way, I'm only 24 and I have excellent health...aside from this of course.